A pitot probe or tube is widely used as part of an aircraft data management system to determine the airspeed of an aircraft. In particular, by measuring stagnation pressure of a fluid driven into the pitot tube, together with a measured static pressure, the airspeed of the aircraft can be determined from the Bernoulli Equation.
A typical pitot tube is a hollow cylinder with heating elements, or coils, arranged internally or externally. The tip portion of the pitot probe is similar to a convergent nozzle consisting of an inlet and throat. The pitot tube inlet diameter can be greater than the throat diameter to improve pressure recovery.
In certain flight conditions, the pitot tube may ingest large amounts of ice crystals or super cooled water droplets which may over power the capacity of the heater to keep the pitot unblocked and ice free. Or melted ice may run back past the high heat tip region of the pitot tube and freeze in a cooler region deep inside the pitot tube blocking the internal air flow and preventing an accurate total pressure measurement. Thus, many pitot probes are not able to pass recent changes to the icing regulations documented in SAE Aerospace Standards AS8006A and AS5562 which represent an increase icing threat. This is because the pitot tube becomes clogged by ice that forms within the internal flow passage of the probe.
The ingested ice crystals and water droplets must be blocked without freezing and prevented from traveling downstream of the Pitot probe where they could plug the Pitot probe and interfere with the total pressure measurement. It is common for pitot tubes to include two dams that are configured to block water droplets and ice crystals from traveling down the internal flow passage of the pitot tube. The dams in the Pitot probe block the water droplets and ice crystals from traveling deep into the probe and direct them to flow out through small drain holes in the pitot tube. Therefore, dams need to be properly oriented and heated to prevent ice buildup within the probe that could block the total pressure measurement.
Additionally it is common to use the same design for several pitot probes that are installed at different locations and orientations on an aircraft. This can cause problems for how ingested water is drained from the probes. Typically, the arrangement of the dams in the internal flow passage of the pitot tube do not have the same effectiveness in all orientations or installations of the pitot probe. Thus, some orientations of the same probe may allow ice to enter the probe more freely and then subsequently be melted by the heater. Furthermore this melted ice may be allowed to flow past the dams to an unheated region of the probe where the water can refreeze and block the pressure measurement. While other orientations may effectively prevent blockages due to icing.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for arrangement of dams in a pitot probe that meet icing regulations for multiple installations and orientations of the same pitot probe.